Lil Bub, the internet's cutest cat, is gone. According to a post by her owner, Mike Bridavsky, Lil Bub died peacefully in her sleep on Sunday, December 1, while battling an aggressive bone infection. Since her birth in June 2011—and particularly after capturing the internet's heart in 2012—she has raised more than $300,000 for animals in need, among other accomplishments.

In 2013, Mental Floss went to Social Tees Animal Rescue for an interview with the feline star and her owner, held in honor of the documentary Lil Bub & Friendz, which was playing at the Tribeca Film Festival that year. Here’s what we learned about the feral cat-turned-internet sensation.

1. Lil Bub's owner said she might have been an alien.

The official story is that Bub was discovered in a rural Indiana tool shed in June 2011, the runt of a litter of feral cats. But Bub didn't look like any of her siblings, Bridavsky told us at the time, "which leads us to believe that she may actually be an alien creature that crashed to Earth, and found this litter of Earth kittens and just joined them to fit in."

2. When she was born, Lil Bub couldn't nurse.

Lil Bub outside Social Tees Animal RescueErin McCarthy

Because of the shape of her mouth, Bub couldn't nurse, so she was bottle-fed until she could eat on her own.

3. When he first saw her, Lil Bub's vet said she was the weirdest cat he had ever seen.

At the time, Bub was 8 weeks old and weighed just 6 ounces, about the size of a Hacky Sack. "He was concerned that with so many birth defects she may not live very long, maybe only a few months," Bridavsky said. "But after doing some tests it turned out she was in good shape!" She and Bridavsky lived a pretty normal life until one of her photos went viral in 2012.

4. A day in Lil Bub's life was pretty regimented.

Lil Bub and owner Mike Bridavsky on her green blanketSamantha Brody for Social Tees Animal Rescue

As of 2013, Lil Bub slept in bed with Bridavsky on her green blanket (which she also traveled with). After waking, they'd take a trip outside so Bub could go to the bathroom. Then Bridavsky mixed Bub's food and medicine, which she ate while he was in the shower. After the shower, he often had to rearrange her food because she liked to smush it. "She’s a lot of work," Bridavsky said, "but I love doing it. It’s great. We have a good relationship."

While Bridavsky prepared the daily Bub blog post, she napped in his lap. Later, they might have shot some photos for the blog or gone outside and hang out.

5. Bub had an extra toe on each foot.

Lil Bub had a total of 22 toes. (Most cats have 18.)

6. After becoming an internet sensation, Bub traveled more than 10,000 miles.

Lil Bub in Bridavsky's armsSamantha Brody for Social Tees Animal Rescue

Lil Bub visited places like New York City, Minneapolis, and Portland. She traveled on the plane with Bridavsky and hung out in her carrier at his feet. "She usually sleeps through the flight," Bridavsky said in 2013. "Airports and everything, she’s totally fine."

7. Bub met many celebrities.

Bub's man celebrity fans included Twilight’s Jackson Rathbone and Robert De Niro, among others. She also appeared on Good Morning America and the Today show.

8. Lil Bub had several medical issues.

Bub had dwarfism, an underdeveloped jaw, and no teeth (that's why her tongue stuck out). She also had osteopetrosis, an exceptionally rare bone disease in cats.

9. Lil Bub loved yogurt.

When Bub wanted to treat herself, she went for one thing: Yogurt. And nothing but Brown Cow yogurt would do.

10. Lil Bub snored. A lot.

For a small cat—she weighed just 3.9 pounds—Bub snored pretty loudly. But it was still adorable.

11. Although she was a cat, Bub preferred dogs.

Here she is meeting Tuna the dog, above.

12. Bub was friends with another internet kitty.

Bub's favorite internet cat/boyfriend was Smoosh, another celebrity feline from Bloomington, Indiana. Smoosh's owner, David, designed much of Bub's merchandise.

13. Most of the proceeds from the sale of Bub's merchandise went to animal shelters in her hometown.

Lil Bub on her green blanketErin McCarthy

The shelters included the Bloomington Animal Shelter, the Monroe County Humane Association, and the Exotic Feline Rescue Center.

Samantha Brody for Social Tees Animal Rescue